1 Field of the Invention
The present invention relates to a computer program product, system, and method for allocating additional requested storage space for a data set in a first managed space in a second managed space.
2 Description of the Related Art
In certain computing environments, multiple host systems may configure data sets in volumes configured in a storage system, such as interconnected storage devices, e.g., a Direct Access Storage Device (DASD), Redundant Array of Independent Disks (RAID), Just a Bunch of Disks (JBOD), etc. Data sets are comprised of extents, which may comprise any grouping of tracks and data storage units. The Z/OS® operating system from International Business Machines Corporation (“IBM”) has a Volume Table of Contents (VTOC) to provide information on data sets of extents configured in the volume, where the VTOC indicates the location of tracks, extents, and data sets for a volume in storage. For Virtual Storage Access Method (VSAM) data sets, the z/OS operating system provides VSAM volume data sets (VVDS) stored in a data set to provide information on VSM key sequenced data sets. (Z/OS is a registered trademark of IBM in the United States and other countries)
Certain volumes may be configured as an extended address volume (EAV) that is divided into a track managed space and a cylinder managed space. In track managed space, storage space on the volume is managed in tracks and cylinders and each data set occupies an integral multiple of tracks. Track managed space also exists in non-EAV volumes. In the cylinder managed space, data in the volume is managed only in units comprising cylinders. A break point value (BPV) may be used to determine whether a request for a data set is directed to the track managed space or cylinder managed space, such that if the size is more than the BPV, the system prefers the cylinder managed space for that extent. This rule applies to each request for primary or secondary space for data sets that are eligible for the cylinder-managed space. If cylinder-managed space is insufficient, the system uses the track-managed space or uses both types of spaces. When the size of a disk space request is less than the breakpoint value, the system prefers to use the track-managed space. If space is insufficient, the system uses the cylinder-managed space or uses both types of spaces.